1. Field of the Invention
The present invention relates, in general, to solid state electrolytic capacitors and structurally improved lead frames used in such capacitors and, more particularly, to a solid state electrolytic capacitor, in which the positive terminal parts of a lead frame assembled with each laminated capacitor unit are bent upward to extend along the front surface of the positive portion of the capacitor unit and are bent rearward to come into contact with the upper surface of the positive portion, thus forming positive terminals of the capacitor unit, and the contact parts of the lead frame extend outward from both sides of the lead frame and are brought into contact with the contact parts of lead frames assembled with the other capacitor units, and the positive portion of each capacitor unit has the same width as that of the other part of the capacitor unit, thus removing stepped corners from the junction of the positive portion and the other part of the capacitor unit, and which is thus not likely to be cracked or broken regardless of impact or load since the capacitor units do not have such stepped corners and are free from undesired stress concentration.
2. Description of the Prior Art
As well known to those skilled in the art, solid state electrolytic capacitors are produced using solid state electrolytes selected from the group consisting of organic materials, such as conductive polymers, and inorganic materials, such as metallic oxides. The solid state electrolytic capacitors are typically fabricated in the form of a laminated structure in an effort to accomplish the requirement of high capacitance. In order to produce such a solid state electrolytic capacitor, a plurality of thin plate type capacitor elements are sequentially layered to form a laminated capacitor unit. Thereafter, several capacitor units having such a laminated structure are layered to form a desired capacitor.
A representative example of conventional solid state electrolytic capacitors is shown in FIG. 1a. As shown in FIG. 1a, a plurality of capacitor units 103 are layered to form a solid state electrolytic capacitor having a laminated structure. Each of the capacitor units 103 is fabricated by layering a plurality of thin plate type capacitor elements 104, and so each capacitor unit 103 also has a laminated structure. Each of the capacitor elements 104 is stepped at corners of an end thereof to form a positive portion 111 of a capacitor unit 103. A lead frame is assembled with the positive portion 111 of each capacitor unit 103, thus forming positive terminals and contacts of the capacitor unit 103. In the lead frame, two positive terminal parts 109 are bent upward and then inward at both sides of the positive portion 111 of the capacitor unit 103. In order to assemble the lead frame with a capacitor unit 103, the lead frame is fitted over the positive portion 111 of the capacitor unit 103 at the positive terminal parts 109. The lead frame also has two contact part parts 108, which are bent downward to be brought into contact with the positive portion 111 of a lower capacitor unit 103. A negative terminal 105 is provided at each side surface of each capacitor unit 103.
FIG. 1b is a plan view of the lead frame of FIG. 1a before the lead frame is assembled with a capacitor unit 103. As shown in this drawing, the positive terminal parts 109 of the lead frame 107 extend in parallel to the contact parts 108. When assembling the lead frame 107 with a capacitor unit 103, the front portion of the frame 107 around the contact parts 108 is bent downward along the dotted line of FIG. 1b such that the contact parts 108 are overlapped with the positive terminal parts 109. Thereafter, the contact parts 108 are bent downward at right angles. Of course, it should be understood that the contact parts 108 are bent upward in the case of a lead frame 107 used with a lowermost capacitor unit 103.
The conventional solid state electrolytic capacitor using such a lead frame is problematic in that it is necessary to bend the contact parts of the lead frame downward to the position under the positive terminal parts prior to laying the positive portion of a capacitor unit on the lead frame during the process of producing the capacitor. Such a step of bending the contact parts undesirably complicates the capacitor production process, and degrades the precision of assembling of the resulting capacitors.
In each of the capacitor elements 104, the part forming the positive portion 111 of a capacitor unit 103 has a width smaller than the xe2x80x9cSxe2x80x9d of the other part of the capacitor element 104, since the lead frame 107 must be bent at both sides of the positive portion 111 of the capacitor unit 103 to form the positive terminals and the contacts of the capacitor unit 103. That is, in order to allow the lead frame 107 to be bent at both sides of the positive portion 111 of the capacitor unit 103 so as to form the positive terminals and contacts without being excessively enlarged in its size, it is necessary to limit the width of the anode portion 111 of the capacitor element such that said width is smaller than that of the other part of the capacitor element 104.
Due to such a width difference between anode portion 111 and the other part of each capacitor element 104, the capacitor element 104 does not form a complete rectangular shape, but undesirably forms stepped corners at the junction between the anode portion 111 and the other part thereof, thus causing stress concentration at said stepped corners. Due to such stress concentration at the stepped corners of each capacitor element, the conventional solid state electrolytic capacitor fabricated using such elements does not effectively resist lateral or vertical impact or effectively endure load applied thereto in a lateral or vertical direction. The capacitor is thus easily cracked or broken.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a solid state electrolytic capacitor and a lead frame used in such a capacitor, in which the lead frame has a simple structure and is designed such that its positive terminal parts are bent at the front of the positive portion of a laminated capacitor unit, thus reducing the number of steps for producing such capacitors, and in which each capacitor element does not have stepped corners at a position around the positive portion.
Another object of the present invention is to provide a solid state electrolytic capacitor, which is not likely to be cracked or broken regardless of impact or load since its capacitor element does not have stepped corners at a part forming the positive portion.
In order to accomplish the above objects, the present invention provides a solid state electrolytic capacitor formed by layering a plurality of capacitor units, each of the capacitor units being fabricated by layering a plurality of plate type capacitor elements and having a positive portion at one end thereof, the capacitor comprising: a lead frame assembled with each of the capacitor units and consisting of: at least one anode terminal parts extending in a forward direction from the lower surface of the capacitor unit, the positive terminal parts being bent to extend upward along the front surface of the positive portion of the capacitor unit, and bent to come into contact with the upper surface of the positive portion, thus forming positive terminals of the capacitor unit; and at least one contact parts extending outward from the lower surface of the capacitor unit in a perpendicular direction to the positive terminal parts, wherein the contact parts of the lead frames respectively assembled with the capacitor units ate in contact with each other, thus bringing the capacitor units into electric contact with each other.
In the solid state electrolytic capacitor, the positive portion of each of the capacitor units preferably has the same width as that of the remaining part of the capacitor unit. The number of the positive terminal parts of the lead frame is preferably set to two, and the two terminal parts are preferably spaced apart from each other by a predetermined gap. Most preferably, the two terminal parts are arranged at positions corresponding to both corners of the positive portion. The contact parts of the lead frames assembled with the capacitor units are preferably bent upward or downward to be brought into electric contact with each other. Alternatively, a part of the contact parts of the lead frames assembled with the capacitor units may extend in parallel to the lower surfaces of the capacitor units, and the rest of the contact parts of the lead frames may be bent upward or downward to be brought into electric contact with each other.
The present invention also provides a lead frame for a solid state electrolytic capacitor, the capacitor being formed by layering a plurality of capacitor units, each of the capacitor units being fabricated by layering a plurality of plate type capacitor elements and having a positive portion at one end thereof, the lead frame being assembled with each of the capacitor units and comprising: a plurality of positive terminal parts extending from the lead frame while being in contact with the front surface of the positive portion of the capacitor unit, thus forming positive terminals of the capacitor unit; and a plurality of contact parts extending outward from the lead frame in a direction perpendicular to the positive terminal parts, and bringing the capacitor units into electric contact with each other.